The present invention relates to seat and back cushions for humans, especially those providing both a cooling function and continuously fluidized coolant material throughout the temperature range in which the cushions will be used.
U.S. Pat. No. 4,508,632 describes a heat storage material which comprises a mixture of sodium sulfate decahydrate or sodium thiosulfate pentahydrate, and urea. The mixing ratio by mole of the sulfate decahydrate to urea is in the range of 1:1 to 1:3 and the mixing ratio by mole of the thiosulfate pentahydrate to urea is in the range of 1:2 to 1:8.
U.S. Pat. No. 4,292,189 describes a thermal energy storage composition that stores heat upon melting and releases heat upon solidification. It is composed of a mixture of sodium sulfate decahydrate, sodium carbonate decahydrate, sodium borate decahydrate and a thickening agent. Its good heat transfer characteristics, relatively high latent heat of fusion, low cost, and favorable melting point allow this material to be particularly useful for space heating applications.
U.S. Pat. No. 4,287,076 describes a method for the storage and conveyance of thermal energy at low temperature, by using the latent heat produced by a substance during changes of state. This substance consists of a salt producing considerable latent heat during change of state, such as Na2SO4.10H2O, combined closely with a nucleating agent such as borax and dispersed in an oil to which an emulsifying agent has been added. This product is particularly suitable for storage of solar energy at low temperature and for heating of enclosed areas.
U.S. Pat. No. 4,964,402 describes an orthopedic device for treatment of injured joints or limbs having at least one gel pad including at least one phase change material for improving the thermal energy storage capacity of the gel pad. The phase change material included in the gel material inside the gel pad may be encapsulated, formed in pellets, soluble, insoluble, or in any desirable form. The gel pad may be removed from the orthopedic device, heated or cooled, and then used with the device for hot or cold therapy of injured joints or limbs, taking advantage of the increased thermal energy storage capacity of the phase change material. Two different phase change materials may be included in the gel pad, one of which may be used for cold temperature therapy while the other is used for hot temperature therapy. The gel pad may include encapsulated water as a phase change material. In addition, a sheet of encapsulated phase change material may be used inside the gel pad which prevents the phase change material from moving inside the gel pad in order to provide a uniform distribution of phase change material inside the pad, resulting in uniform temperature distribution for hot or cold therapy.
U.S. Pat. No. 5,456,852 describes a microcapsule for heat-storing material which encapsulates a compound capable of undergoing phase transitions, said microcapsule containing a high-melting compound having a melting point 20.degree.-110.degree. C. higher than that of the compound capable of undergoing phase transitions.
U.S. Pat. No. 4,671,267 describes the use of a pliable, self-sustaining, moisture sorbing gel including a humectant such as glycerin entrapped within a synthetic resin polymer matrix (e.g., a matrix containing acrylic acid or acrylamide monomer moieties). In one preferred embodiment, a body of the gel is encased within heat and moisture-permeable stretch fabric, and securing ties or the like are provided to permit the composite to be conformed to a body part and held in place. In use, such therapy wraps are either heated (as in a microwave oven) or refrigerated, so as to provide appropriate thermal treatment; it has been found that the preferred gel of the invention retains its pliability and other physical properties over a very broad temperature range, such as -20.degree. to 305.degree. F., and therefore the wraps of the invention can be used in many treatment contexts. It has also been discovered that the gel material can be applied directly to injured skin to in effect create a temporary skin with ideal air permeability. Furthermore, the moisture absorbing and desorbing properties of the gel create a moisture equilibrium between the gel, damaged skin and the atmosphere, thus promoting rapid healing.
The following table comprises some common materials whose solid--liquid phase transition temperature ranges have been found to have application in direct or sheathed contact with human skin for one or more uses:
______________________________________ Phase Change Material Type MP (.degree. C.) ______________________________________ MgCl2.6H2O Quasicongruent 117 Mg(NO3).6H2O Congruent 89 Na4P2O7.10H2O Incongruent 70 NaOAc.3H2O Incongruent 58 MgCl2.6H2O/Mg(NO3)2.6H2O Eutectic 58 Paraffin wax Congruent 50 Na2S2O3.5H2O Semicongruent 48 Neopentyl glycol Congruent 43 CaBr2.6H2O Congruent 34 Na2SO4.10H2O Incongruent 32 CaCl2.6H2O Semicongruent 28 Polyethylene glycol Congruent 23 Na2SO4.10H2O/NaCl Incongruent 18 CaBr2.6H2O/CaCl2.6H2O Isomorphous 15 Na2SO4.10H2O/KCL/NH4Cl Incongruent 8 ______________________________________
Na2SO4.10H2O is not associated with uses for cooling upon consideration of its melting temperature just under the normal temperature for humans. Such a phase change material is considered in the prior art to have mostly use in the area of heat treatment gel pads applied to the skin surface.